Method for coating corrugating rolls using high velocity oxygen fueled thermal spray

Abstract

A method for forming a hardened coating on a workpiece, such as a corrugating roll, having an undulated surface. A high velocity oxygen fueled gun is aligned with the undulated surface and a coating material is sprayed onto the surface from the gun to form a hardened coating having substantially uniform surface characteristics. The coating material is a tungsten carbide-cobalt material, or other hard carbide or oxide materials, which is sprayed onto the surface in a direction which is parallel to and offset from a plane passing through the longitudinal center of the roll. During the spraying operation, the gun is traversed along the length of the roll while the roll is rotated.

What is claimed is: 
     
       1. A method of forming a hardened coating on a substantially cylindrical workpiece defining a longitudinal axis extending through the center of the workpiece and having an undulated surface, the method comprising the steps of: aligning a nozzle of a high velocity oxygen fueled gun with said undulated surface; and   spraying a coating material onto said surface from said gun to form a hardened coating;   wherein said undulating surface includes a plurality of elongated tips and gullets extending in a longitudinal direction, and flanks extending between adjacent tips and gullets, and said hardened coating is deposited to a substantially uniform thickness on said tips, gullets and flanks during said spraying step; and   said step of aligning said nozzle of said gun comprises aligning a centerline of the outlet of said nozzle along a line displaced from said longitudinal axis whereby said centerline of the outlet said nozzle is aligned substantially parallel to at least one of said flanks and such that said at least one flank is located in an area being sprayed with said coating material.   
     
     
       2. The method as in claim 1 wherein said coating material is a tungsten carbide-cobalt material. 
     
     
       3. The method as in claim 2 including the step of honing said coating material. 
     
     
       4. The method as in claim 1 including the step of traversing said gun along said longitudinal axis during said step of spraying said coating material. 
     
     
       5. The method as in claim 1 wherein said spraying step comprises spraying a flank adjacent to said at least one flank while leaving said at least one flank substantially uncoated and, subsequently, redirecting said nozzle to coat said at least one flank. 
     
     
       6. The method as in claim 5 including the step of traversing said gun along said longitudinal axis during said step of spraying said coating material. 
     
     
       7. The method as in claim 6 including the step of rotating said workpiece about said longitudinal axis during said step of traversing said gun. 
     
     
       8. The method as in claim 6 wherein said step of aligning said nozzle of said gun comprises aligning said centerline of the outlet of said nozzle in spaced relation to a side of a plane passing diametrically through said roll and extending parallel to and containing said longitudinal axis and directing said nozzle to spray parallel to said plane, and subsequently, moving said centerline of the outlet of said nozzle into spaced relation to an opposite side of said plane. 
     
     
       9. The method as in claim 1 wherein said workpiece is a corrugating roll and said coating material is a tungsten carbide-cobalt material. 
     
     
       10. A method of coating a corrugating roll defining a longitudinal axis extending through the center of the corrugating roll and said corrugating roll having an undulated surface defined by alternating tips and gullets with flanks extending between said tips and gullets, the method comprising the steps of: aligning a nozzle of a high velocity oxygen fueled gun with said surface;   spraying a tungsten carbide-cobalt material onto said surface from said gun to form a hardened coating having substantially uniform surface characteristics; and   wherein said step of aligning said nozzle of said gun includes aligning a centerline of the outlet of said nozzle along a first line extending transverse to a line extending from said nozzle diametrically through said roll whereby said centerline of the outlet of said nozzle is aligned substantially parallel to at least one of said flanks and such that said at least one flank is located in an area being sprayed with said coating material.   
     
     
       11. The method as in claim 10 including the step of traversing said gun along said longitudinal axis during said step of spraying said material. 
     
     
       12. The method as in claim 11 including the step of rotating said roll in a first direction about said longitudinal axis during said step of spraying said material. 
     
     
       13. The method as in claim 12 including the step of aligning said centerline of the outlet of said nozzle along a second line extending transverse to a line extending from the outlet of said nozzle diametrically through said roll and rotating said roll in a second direction opposite to said first direction during said step of spraying said material. 
     
     
       14. The method as in claim 13 wherein said gun traverses said roll a plurality of times and said roll rotates a plurality of times during each traverse of said gun. 
     
     
       15. The method as in claim 10 wherein said step of aligning said nozzle further includes locating said nozzle in a first position in spaced relation to a side of a plane passing diametrically through said roll and extending parallel to and containing said longitudinal axis and aligning said centerline of the outlet of said nozzle parallel to said plane. 
     
     
       16. The method as in claim 15 wherein said step of aligning said nozzle further includes moving said nozzle to a second position in spaced relation to an opposite side of said plane and aligning said centerline of the outlet of said nozzle parallel to said plane. 
     
     
       17. The method as in claim 16 including the step of rotating said roll during said step of spraying said material, wherein said roll is rotated in a first direction when said nozzle is located in said first position, and said roll is rotated in a second opposite direction when said nozzle is located in said second position.